It is not hard at all to find overseas banks that are paying 10% or more. To deposit money in a foreign currency you will lose around 5% of your capital in exchange costs and the same again on any withdrawals. That might leave you with a small gain over a year but that could be turned into a sterling loss by currency fluctuations. In any country with high inflation, currency fluctuations are most likely to move against you.

To approach answering your question, as you know, some UK banks are safer than others. If you read the UK financial press, you will have a good idea which ones are the more solid ones. Similarly, if you read the Turkish financial press, you might get an idea about which banks there are solid (and no, it's not just a matter of seeing who is biggest or what depositor guarantees are in place).

I would expect that most mainstream Turkish accounts are only available to Turkish residents. If you find one who is encouraging overseas investments, it may be a scam.